1. Field of the Invention
This invention relates to a fluidized crusher/drier for use in a fluidized crushing/drying system for crushing industrial waste, in particular, moisture-containing industrial waste, then exposing it to high-speed hot blast, and finally recovering it in the form of dried particles or powder.
2. Prior Art
A patent publication of Japanese Patent No. 1290498 discloses a fluidized crusher/drier for use in a fluidized crushing/drying system. The prior art crusher/drier includes a tower-shaped housing, a product discharge outlet at the top of the housing for communication with a product recovery unit through a duct, a material inlet provided at a lower portion of the housing for entry of industrial waste or the like (hereinafter called a material) to be treated, a hot blast inlet provided at a lower portion of the housing, and two crusher vane wheels provided along the bottom of the housing for rotation in opposite directions.
Pulverization of a material by using the prior art fluidized crusher/drier is performed as follows: The material is continuously supplied through the material inlet onto the vane wheels, and it is broken from a large mass into small masses or lumps while blowing hot blast thereto. Such small masses or lumps are repelled upward by crusher vanes of the crusher vane wheels and are recrushed into small lumps, grains or particles due to collision between them. Meanwhile, moisture evaporates from the material, and dried particles or powder are conveyed upward by air flow supplied for drying purposes. Semi-treated part of the material still in the form of coarse wet lumps, masses or grains that have failed to ride on the fluidized air flow drop onto the vane wheels and again undergo the same treatment. By repeating this procedure, the material is finally crushed into particles or powder which are fine enough to ride on and move up with ascending air flow caused by hot blast blown into the fluidized crusher/drier. The particles and powder are discharged through the product discharge outlet and the duct, and are recovered by the recovery unit.
The prior art fluidized crusher/drier, however, is not satisfactory in efficiency of pulverization, due to various problems explained below.
Namely, it uses two crusher vane wheels. The use of two crusher vane wheels invites an interference loss.
Semi-treated part of the material in the form of lumps, grains or particles still having large apparent specific gravities and metal scraps or other debris contained in the material which have been repelled at a high speed to an upper portion of the housing by the crusher vane wheels often fail to fall onto the crusher vane wheels, but run to the discharge outlet at the ceiling and enter in the recovery unit through the duct.
The material crushed into lumps or grains and repelled by the crusher vane wheels may hit and damage bearings of the crusher vane wheels and their adjacent wall surfaces. Moreover, relatively small grains or particles may be blown to the exterior through gaps around the bearings received in bores in the housing wall.
Some of coarse grains or particles that have failed to ascend together with the air flow may remain under the crusher vane wheels and increase the load to the crusher vane wheels, which necessarily increases the power. In particular, pebbles, nails, staples or other debris contained in the material supplied to the fluidized crusher/drier are apt to remain around the lower halves of the crusher vane wheels, and they often engage between the crusher vanes of the crusher vane wheels and the bottom surface. Then they damage vanes of the crusher vane wheels or increase the load to the crusher vane wheels.
Such increase in load to the crusher vane wheels, in turn, increases the load to the drive source, and may accidentally interrupt rotation of the crusher vane wheels. When such a trouble occurs, it is necessary to stop the operation to remove the debris. However, interruption of operation causes all the material under crushing treatment to accumulate on the bottom surface and on the crusher vane wheels, and the debris must be removed under such a bad condition. Therefore, much time and labor are required for removal of debris.